Reviewed by USGSBulgaria124y ago
M6.8 earthquake 6 km W of Stara Kresna, Bulgaria
Monday, April 4, 1904, 10:02:34 UTC · 41.802°N, 23.108°E
A magnitude 6.8 earthquake struck 6 km W of Stara Kresna, Bulgaria on Monday, April 4, 1904, 10:02:34 UTC, at a depth of 15.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 6.8
- Strong · mw
- Depth
- 15 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
274 kilotons of TNT
That is about 18 times the Hiroshima bomb. It released about 575 times the energy of a magnitude 5.0.
Tectonic setting
221 km
from the nearest mapped plate boundary, between the Aegean Sea and Eurasian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
15 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 100 km
USGS lists 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M7.0 on April 4, 1904. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists no earlier M5.0+ earthquakes within 300 km.
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 16 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 6 recorded deaths. The most severe:
- 1902M6.5
Thessaloniki
5 Jul 1902 · 109 km away · intensity IX
5 deathsModerate damage ($1–5M)tsunami
- 1893M6.5
Samothraki
9 Feb 1893 · 247 km away · intensity X
1 deathModerate damage ($1–5M)tsunami
- 1904M7.8
Struma
4 Apr 1904 · 8 km away · intensity XI
Severe damage ($5–24M)
- 1904M7.5
Struma
4 Apr 1904 · 8 km away · intensity X
Severe damage ($5–24M)
- 1750
Plovdiv
Oct 1750 · 144 km away · intensity X
Severe damage ($5–24M)tsunami
- 1759
Thessaloniki; Bulgaria: Plovdiv
26 Jun 1759 · 116 km away
Severe damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.